AM1 STUDY ON THE CONFORMATIONS OF ZWITTERIONS OF BENZYLPENICILLIN LACTIM TAUTOMER

The conformation and electronic structure of zwitterions of benzylpenicillin lactim tautomer have been optimized and calculated in the gas phase by semi-empirical molecular orbital AM1 method usually considering an isolated molecule surrounded by vacuum. The formation of zwitterions of benzylpenicillin lactim tautomer has been studied by comparison of the different positions of net charges on nitrogen atoms in the molecule. In this connection, the heats of formation (∆Hf o ), dipole moment (μ), full atomic charges and energies of frontier molecular orbitals (EHOMO and ELUMO) have been performed and discussed. The effect of conformational changes and their stabilities have been determined.